A lysimeter is a hydrologic measuring instrument used to monitor the transmission rate and/or presence of fluid in soil or like substrates. The lysimeter accomplishes this function by application of vacuum principles causing the fluid to be drawn toward the lysimeter. Removal of collected fluid from the lysimeter may be by any one of a number of methods.
Heap leaching is a process used to recover materials from ore and the like. Typically, a trench is dug into the ground and the sides thereof are lined with an impermeable barrier. The ore to be treated is placed into the trench, as are appropriate solubilizing chemicals. The solubilizing chemicals, typically, are toxic, and leakage thereof into the earth is to be avoided. An exemplary disclosure of a heap leaching system is found in Johnson, U.S. Pat. No. 4,526,615 for CELLULAR HEAP LEACH PROCESS AND APPARATUS, which patent discloses the use of a perforated pipe to collect leach solution draining from the impermeable barrier.
Detection of the leakage of toxic chemicals from the heap leach pad is important if such processes are not to cause environmental damage. the heap leach pad can cover a rather large area, and it is necessary that a leak be detected relatively quickly in order to avoid damage to surrounding soil. It is furthermore important that the location of a leak be determined with relative accuracy in order to permit suitable repairs to be made with a minimum amount of disruption to the overall leaching system.
Naturally occurring soil is subject to numerous inconsistencies caused by discontinuities in the soil. Further inconsistencies are caused by rocks, other foreign matter and the like. Such inconsistencies can give rise to channeling of whatever fluids may be percolating through the substrate, thereby giving rise to errors in site location should leak detection be attempted.
The disclosed invention is a lysimeter specifically directed towards use with a heap leaching system in order to permit accurate detection and location of leach pad leaks. The lysimeter causes a vacuum to be applied to a prepared granular substrate which avoids channeling, filters particulates to prevent clogging of the lysimeter and provides a uniform medium for vacuum transmission. The lysimeter of the invention is relatively inexpensive to manufacture, may be interconnected into a series of lysimeter strings extending the length of each leach pad, and the individual lysimeters can be selectively addressed in order to permit the site of a leak to be accurately and quickly identified.